LOCATION BROADWELL ILEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Typic Argiudolls
TYPICAL PEDON: Broadwell silt loam - on a gently sloping knoll in a cultivated field at an elevation of 625 feet. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 9 inches; very dark grayish brown (10YR 3/2) silt loam, brown (10YR 5/3) dry; weak fine granular structure; friable; common very fine roots and few fine roots; moderately acid; clear smooth boundary.
A--9 to 15 inches; very dark grayish brown (10YR 3/2) silt loam, brown (10YR 5/3) dry; moderate fine granular structure; friable; few very fine and fine roots; slightly acid; clear smooth boundary. (Combined thickness of the A horizons is 10 to 20 inches)
Bt1--15 to 18 inches; dark brown (10YR 3/3) silty clay loam, yellowish brown (10YR 5/4) dry; weak very fine and fine subangular blocky structure; friable; few very fine and fine roots; many faint very dark grayish brown (10YR 3/2) organ-clay films on faces of peds; slightly acid; clear smooth boundary.
Bt2--18 to 25 inches; brown (10YR 4/3) silty clay loam; moderate fine subangular blocky structure; firm; few very fine and fine roots; common faint very dark grayish brown (10YR 3/2) organo-clay films on faces of peds; moderately acid; clear smooth boundary.
Bt3--25 to 31 inches; brown (10YR 4/3) silty clay loam; moderate fine subangular blocky structure; firm; few very fine and fine roots; common faint very dark grayish brown (10YR 3/2) clay films in root channels and/or pores and common faint brown (10YR 4/3) clay films on faces of peds; moderately acid; clear smooth boundary.
Bt4--31 to 41 inches; dark yellowish brown (10YR 4/4) silty clay loam; moderate medium subangular blocky structure; firm; few very fine and fine roots; few distinct very dark grayish brown (10YR 3/2) clay films in root channels and/or pores and common faint brown (10YR 4/3) clay films on faces of peds and few distinct light gray (10YR 7/2) silt coatings on faces of peds and in pores; moderately acid; clear smooth boundary.
Bt5--41 to 50 inches; dark yellowish brown (10YR 4/4) silt loam; weak medium and coarse subangular blocky structure; friable; few very fine roots; common faint brown (10YR 4/3) clay films on faces of peds; few distinct light gray (10YR 7/2) silt coatings on faces of peds and in pores; few fine faint brown (10YR 5/3) masses of iron accumulation along micropores; moderately acid; abrupt smooth boundary. (Combined thickness of the Bt horizons is 20 to 40 inches)
2BC1--50 to 55 inches; dark yellowish brown (10YR 4/4) stratified loamy fine sand and sandy loam; weak coarse subangular blocky structure; very friable; slightly acid; clear smooth boundary. (Combined thickness of the 2BC1 and/or 2Bt horizons is 0 to 14 inches)
2BC2--55 to 76 inches; stratified yellowish brown (10YR 5/4) and brown (7.5YR 4/4) fine sand and loamy sand; single grain; loose; few distinct dark brown (7.5YR 3/2) organic coatings in pores; three inch band of yellowish brown (10YR 5/6) silt loam starting at 75 inches; neutral; clear smooth boundary. (Combined thickness of the 2BC2 horizon is 0 to 30 inches)
2C--76 to 80 inches; yellowish brown (10YR 5/4) fine sand; single grain; slightly acid.
TYPE LOCATION: Christian County, Illinois; about 1 mile northwest of Mount Auburn; 2500 feet north and 460 feet west of the center of section 11, T. 15 N., R. 2 W.; U.S.G.S. Mount Auburn topographic quadrangle; lat. 39 degrees 46 minutes 17 seconds N. and long. 84 degrees 16 minutes 51 seconds W., NAD 27.
RANGE IN CHARACTERISTICS: The solum is 45 to 80 inches in thickness. The loess is 40 to about 60 inches in thickness over the loamy sand or sand. The mollic epipedon is 10 to 20 inches in thickness. The upper 20 inches of the argillic horizon averages more than 27 percent clay and less than 10 percent sand.
The Ap or A horizon has hue of 10YR, value of 2 or 3, and chroma of 1 to 3. The texture is silt loam. It is moderately acid to neutral.
Some pedons have an AB or BA horizon.
The Bt horizon has hue of 10YR or 7.5YR, value of 3 to 5, and chroma of 3 to 6. The texture is dominantly silty clay loam, but is silt loam in the upper or lower parts of some pedons. Reaction is moderately acid or slightly acid in at least one subhorizon, and is neutral in the upper part or in the lower part in some pedons. Some pedons do not have redoximorphic features in the lower part of the Bt.
The 2Bt horizon, where present, and 2BC horizon has hue of 10YR or 7.5YR, value of 4 or 5, and chroma of 4 to 6. The 2Bt horizon and upper part of the 2BC horizon is typically stratified clay loam, loam, silt loam, fine sandy loam or loamy sand. The lower part of the 2BC horizon is typically loamy sand or loamy fine sand, but some pedons are fine sand or sand. Reaction is moderately acid to neutral.
The 2C horizon is present above a depth of 60 inches in some pedons and has hue of 10YR or 7.5YR, value of 4 or 5, and chroma of 4 to 6. It is fine sand, sand, loamy fine sand or loamy sand. Clay content ranges from 3 to 10 percent. Sand content ranges from 50 to 90 percent and averages more than 80 percent. Reaction is moderately acid to neutral.
COMPETING SERIES: These are the Ashdale, Dinsdale, Douglas, Elkhart, Elmont, Healing, Lycurgus, Malcolm, Meadowbank, Mendota, Mickle (T), Ogle, Osco, Parkway, Plano, Proctor, Richwood, Ripon, Sibley (see Remarks), Sidell, Tama, Tecumseh, Toddville, Wakenda, Waupecan, and Wiota series. Ashdale soils have more than 35 percent clay in the lower part of the series control section. Dinsdale, Meadowbank, Mendota, Proctor and Tecumseh soils have less than 40 inches of loess. Sibley soils have mollic epipedons more than 24 inches in thickness. Douglas, Healing, Ogle, Osco, Parkway, Sidell, Tama, Wakenda and Wiota soils have more than 10 percent clay and less than 50 percent sand in the lower part of the series control section. Elkhart soils have carbonates within a depth of 40 inches. Elmont soils have a paralithic contact within a depth of 60 inches. Lycurgus soils have more than 10 percent sand in the upper part of the series control section. Malcolm soils formed in noncalcareous interglacial sediments and have sola less than 40 inches. Mickle (T), Richwood and Toddville soils average less than 27 percent clay in the particle-size control section. Plano soils average 3 percent or more rock fragments and less than 80 percent sand in the lower part of the series control section. Ripon soils have a lithic contact within a depth of 40 inches. Waupecan soils contain more than 15 percent rock fragments in the lower part of the series control section and have carbonates within a depth of 60 inches.
GEOGRAPHIC SETTING: Broadwell soils are on nearly level to rolling uplands near stream valleys. They formed in 40 to 60 inches of loess and in the underlying eolian loamy sand or sand. Slope gradients range from 0 to 12 percent. Mean annual temperature ranges from 50 to 54 degrees F, and mean annual precipitation ranges from 32 to 36 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Lawndale, Pillot, Sable and Tama soils. The somewhat poorly drained Lawndale soils are on lower lying or more nearly level areas nearby and form a hydrosequence with Broadwell soils. Tama soils are on similar landscapes nearby where loess is more than 60 inches in the thickness. Pillot soils are nearby where loess is thinner; they have strongly contrasting particle-size class of fine-silty over sandy or sandy-skeletal. Poorly drained Sable soils are nearby in lower lying areas. They have grayer colors throughout.
DRAINAGE AND PERMEABILITY: Well drained. The potential for surface water runoff is low on nearly level areas and medium on sloping areas. Permeability is moderate in the upper part of the solum and moderately rapid or rapid in the lower part and in the substratum.
USE AND VEGETATION: Most areas are cultivated. Corn, soybeans and small grain are the principal crops. Meadow is grown for hay in some areas. The native vegetation is prairie grasses.
DISTRIBUTION AND EXTENT: Central Illinois in MLRA 108A and 108B. Extent is moderate.
MLRA OFFICE RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Logan County, Illinois, 1976
REMARKS: Diagnostic horizons and features recognized in this pedon are: Mollic epipedon - the zone from the surface to a depth of 18 inches (Ap, A and Bt1 horizons). Argillic horizon - the zone from approximately 15 inches to 50 inches (Bt1, Bt2, Bt3, Bt4 and Bt5 horizons). Udic soil moisture regime.
This update (8/2003) relocates the typical pedon from Sangamon County, Illinois to a more representative site in Christian County, Illinois.
The Sibley soils should be reclassified as Pachic Argiudolls and, therefore would not be a competing series.